There are two channels, the conda channel maintained by the Anaconda company and the conda-forge channel maintained by the community. Unfortunately in the case of Spyder, the Anaconda company are many months behind... and therefore you won't find the current version of Spyder Kernels when using their default channel.
You may also find some conflicts when attempting to install conda-forge packages into the Anaconda base conda environment. For the latest version of Spyder, you are better to make a new conda environment which includes spyder and the required packages and optional packages from the conda-forge channel. Use:
conda create -n spyder-cf
conda activate spyder-cf
conda install -c conda-forge spyder
conda install -c conda-forge cython seaborn scikit-learn sympy openpyxl xlrd xlsxwriter lxml sqlalchemy
If it helps I made an installation video covering installation of the latest version of Spyder in Windows and Linux using Miniconda here: